Hopes for defusing the Iranian nuclear crisis were thwarted Wednesday when the International Atomic Energy Agency (IAEA) said Iran did not agree to clear up nuclear weapons allegations and refused access to a site during a visit by senior agency officials.

“It is disappointing that Iran did not accept our request to visit Parchin during the first or second meetings,” said IAEA Director General Yukiya Amano, referring to a military site where a simulated nuclear warhead was allegedly tested.

“We engaged in a constructive spirit, but no agreement was reached,” he said.

His statement came hours before a senior team of IAEA officials was expected to return from Tehran to Vienna after a second round of talks with Iranian nuclear officials that was accompanied by rising tensions between Iran and Israel.